Mixing equipment ribbon mixer

Numerous equipment types can be used for agglomeration, including horizontal ribbon and vertical mixers, rotary drums, zig-zag mixers, and pan agglomerators. Horizontal ribbon mixers as shown in Fig. 36.41 are used primarily for dry mix formulating, where only limited agglomeration occurs. They are comprised of a U-shaped trough and a ribbon or paddle-type agitator. Liquids are sprayed onto the surface of the dry material and slowly dispersed into the mix. Mixer operations can be either batch or continuous. 

Scott and Macosko [1991] proposed a mechanism of the morphology development based on experiments carried out in a batch mixer. When the minor component pellet melts, sheets or ribbons of the dispersed phase are formed due to dragging of the pellets on the hot surface of the mixing equipment. Next, holes are formed in the sheets or ribbons of the dispersed phase, as the interfacial instability starts, and, sheet or ribbon morphology changes into a lace structure. Then, the lace breaks into irregularly shaped pieces with diameters equal to the ultimate sphere morphology. 

Mixing Mechanisms Consider a calendering process for manufacturing PVC floor covering. The line consists of a ribbon-type blender in which the PVC is dry-blended, and an internal mixer that feeds a SSE equipped with a static mixer, feeding the first nip of the calender. What types of mixing mechanisms does the polymer experience Specify the locations at which each mechanism occurs. 

A torque rheometer is used to determine fusion characteristics of PVC compounds. Components of formulation are first mixed in a beaker in an intensive mixer or ribbon blender. The rheometer is equipped with roller head and the premixed sample is added to a chamber having preselected temperature (typical temperatures used are 140 for flexible compounds, 180 for semirigid compounds, and 197°C for rigid compounds). The amount of the sample added is selected such that it occupies 65% of mixer bowl. Mixing is continued until torque peak is reached. Mixing time and maximum torque are two important results of testing. 

This type of mixer has a reduced efficiency, but it can be improved by changing the drum shape or by equipping it with baffles [53, 55]. There are several types of constructive solutions for mechanical mixers, such as intensive nonfluxing mixers, ribbon blenders, double arm mixers, plug mixers, etc. [42, 55-57]. They assure mixing both at room temperature and at high temperature moreover, in some of them, the obtained mixture can be cooled [42] these make them suitable for various forms of the mixing components [42, 55]. 

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